Officials at the Food and Drug Administration in October said they were investigating five deaths and a nonfatal heart attack that happened within a three-year period that may be linked to energy drink ingestion. In its coverage of the investigation, the New York Times said the number of reports that the FDA receives about any product it regulates usually understates by a large degree the actual number of problems.

A person’s reaction to caffeine depends on how much he or she usually drinks, his or her age, body mass, medication use and other health conditions, according to the Mayo Clinic. Too much can cause: